Electrically Induced Blink for the Prevention of Ocular Symptoms and Blurred Vision in Patients With Acute Facial Nerve Palsy

Abstract

Objectives: Facial nerve palsy causes blurred vision and ocular discomfort due to deficits in blinking and eye closure. The objective of this study was to determine whether eye-blinks could be elicited by electrical stimulation and whether electrically induced blink would have an effect on the visual acuity and ocular symptoms in patients with acute facial nerve palsy. Methods: The zygomatic branch of the facial nerve of fifteen participants with acute facial nerve palsy was electrically stimulated in order to elicit a blink. In successful cases, the participant proceeded with a two-hour TV watching session in which an electrically induced blink was delivered every 5 seconds. The control condition consisted of an otherwise similar TV watching session without electrically induced blinking. Subjective ocular symptoms were evaluated with a Dry Eye Questionnaire and visual acuity was assessed with a Logarithm of the Minimum Angle of Resolution (LogMAR) chart before and after both sessions. Results: The stimulation produced a blink in 8 participants (53%). The visual acuity in the affected eye decreased during the control session, whereas no significant change occurred during the stimulation session. The ocular symptoms were significantly reduced during the stimulation session. Conclusions: Electrically elicited blink is a promising method for reducing the eye symptoms in individuals with acute facial nerve palsy.

Bionic blink improves real-time eye closure in unilateral facial paralysis

“…NEURO-BLINK increased eye closure and cornea coverage in eight patients who had a functional response to electrical stimulation eliciting unnatural, but not uncomfortable sensations. The most common electrode placement to best induce a blink was lateral to the eye, consistent to what was found by previous studies [26,28]. However, we also present an alternative optimal bottom location that proved especially assistive in patients who had residual muscle activity in response to an intentional blink movement mainly in the upper lid.…”

“…Electrodes 1.5 cm in diameter were used to elicit a blink in subjects. The active electrode was placed on the paretic side at the innervation point of zygomatic branch to the OOM just lateral to the orbital rim [26].…”

“…Stimulation frequency and duration were kept constant at 100 Hz and 100 ms respectively, which according to previous studies mimic a natural blink [26,28]. To determine the best location, the cathode of the stimulating electrode pair was placed in the corner of the eye to target the innervation point of the zygomatic branch of the facial nerve on the OOM [26][27][28]. Positions of the stimulating anode were: +90 • , +60 • , +30 • , 0, −30 • , −60˚, −90 • , −120 • as well as electrodes under eye with cathode below the orbital rim (position called 'under 1') and electrodes under eye shifted 1 cm towards the nose compared to 'under 1' (position called 'under 2').…”

“…During this calibration phase, charge magnitude (amplitude and pulse width) and electrode locations were varied to determine the optimal parameters (figure S3). Stimulation frequency and duration were kept constant at 100 Hz and 100 ms respectively, which according to previous studies mimic a natural blink [26,28]. To determine the best location, the cathode of the stimulating electrode pair was placed in the corner of the eye to target the innervation point of the zygomatic branch of the facial nerve on the OOM [26][27][28].…”

“…Electrical stimulation has also been used to improve facial function through non-invasive activation of muscles [23]. Although electrical stimulation has not demonstrated significant therapeutic effects in improving facial muscle function [24,25], it shows promise as an assistive tool to restore both blink function [26][27][28] and facial muscle tone [15] without surgery in acute cases (2-3 months) [26,28]. Moreover, restoration of the blink function was shown to improve visual acuity as well as ocular symptoms such as foreign body sensation and dryness after a few hours [26,27].…”